Showing posts with label mobile. Show all posts
Showing posts with label mobile. Show all posts

Wednesday, July 18, 2012

What Is GSM?

GSM, or Global System for Mobile Communications, is a cellular phone protocol that is standard in most parts of the world. Technology experts created the protocol in the 1980s and ’90s to standardize cellular phone service between countries in Europe. GSM phones use subscriber identity module (SIM) cards, which is essential to their function and enable the user to change phones easily. It is a chief competitor to the Code Division Multiple Access (CDMA) protocol.

Technology

Technically, the term GSM refers to second-generation (2G) voice networks that operate based on a combination of time division multiple access (TDMA) and frequency division multiple access (FDMA). TDMA takes the frequency channel the phone uses and divides it into individual bits of time that are assigned to each user. FDMA divides the frequency band into sections and assigns one to each cell phone tower. Towers are typically spread far enough apart so that those using the same frequency do not overlap their areas of coverage.

The term “GSM” is also used to refer to third-generation (3G) technology put into place by the same companies and using the same underlying network. This is actually called Universal Mobile Telecommunications System (UMTS), and uses the Wideband CDMA (W-CDMA) air interface standard in most places. Although they are both spread spectrum technologies, W-CDMA and the standard used by competing CDMA phones (usually CDMA2000) are not compatable.

GSM and CDMA

Although both refer to cellular phone networks, GSM and CDMA differ in the technology that they use. CDMA uses a system in which all signals are sent at the same time, but each is spread across multiple frequencies. Servers assign an individual code to each transmission so that the signals don’t interfere with each other and can be matched up between the sender and receiver.

Originally, the two protocols differed in signal quality, consistency, and voice distortion, among other features. Both methods have been improved, however, and there are few significant differences between the two in terms of call quality. GSM phones are slightly more likely to drop calls as a user moves between cell towers, but they have better coverage in places with a lot of mountains. This technology also allows for voice and data transmission at the same time, which most CDMA phones cannot do.

In some parts of the world, both services are available, but one tends to be more common than the other. Most cellular service providers only use one type of network because it’s very expensive to maintain both types of service. GSM is the older service, and is found in most places around the world, while CDMA is most common in the US and Asia.

SIM Cards

GSM phones use a SIM card, which is a small card with an embedded integrated circuit that stores personal data, the user’s phone number, account information, and contacts. When a user switches phones, exchanging the SIM card from one phone to the other transfers the cell service and phone number, and activates the new phone. The contact list, calendar, and other personal data is usually easily moved between handsets.

Data Transfer Information

The 2G system is capable of data transmission speeds of up to 14.4 kilobits per second (kbps). Originally, not all networks had this capability, but continued advances and improvements in the system have raised speeds. 3G systems, which are designed specifically for mobile Internet and video, can transfer data much more quickly; depending on the interface, theoretical download speeds range from 2 megabits per second (Mbps) to 56 Mbps.

Frequencies

The frequency band used by these phones depends on several factors, including the location and technological changes. For example, in Europe, 2G GSM networks operate in the ranges of 900MHz and 1,800MHz and 3G networks use the 2,100 MHz band. The United States operates on frequencies in the range of 850MHz and 1,900MHz. Many other countries, including Australia and some places in South America, use the 850 MHz range. Most phones are designed for the countries where they are used most often, but a quad-band handset will handle 850, 900, 1,800, and 1,900MHz, and usually work in most areas.

Coverage

As of 2011, most countries from the Arctic region to Antarctica use the GSM protocol. It’s particularly common in Europe, where it originated, and most of the Eastern hemisphere generally, including many developing countries. In the Western hemisphere, the CDMA protocol is more common in the United States and a few other countries. However, many countries, including Canada and Brazil, use GSM.

History

The European Telecommunications Standards Institute (ETSI) created GSM to standardizemobile phone communications among European nations; before this, each country had its own protocol. Standardizing the technology created a large, growing pool of users, and the protocol spread throughout the world. In 2002, approximately 70% of cellular phone clients worldwide used GSM services, while about 12% used CDMA. By early 2010, the GSM Association stated that there were over 4 billion users, and they estimate that there will be over 6 billion by 2015.

Thursday, December 16, 2010

"ICE" campaign : very important to read

Isn't it true that we all carry our mobile phones with hundreds of names/numbers stored in its memory but yet nobody, other than ourselves, know which of these numbers belong to our near and dear ones? 

Let us for a moment create a scenario wherein (God forbid) we are involved in an accident or had a heart attack and the people attending to us get hold of our mobile phone but don't know which number to call to inform our family members. 

Yes, there are hundreds of numbers stored but which one is the contact person 
in case of an emergency? For this reason, we must have one or more telephone numbers stored under the name ICE (In Case of Emergency) in our mobile phones. 

Read below for more details. 

Fwd: " ICE" Campaign 

Recently, the concept of "ICE" is catching up quickly. It is simple, an important method of contact during emergency situations. As cell phones are carried by majority of the population, all you need to do is store the number of a contact person or person who should be contacted during emergency as "ICE" 
(meaning In Case of Emergency). 


The idea was thought up by a paramedic who found that when they went to the scenes of accidents, there were always mobile phones with patients, but they didn't know which number to call.

He therefore thought that it would be a good idea if there was a nationally recognized name for this purpose.

Following a disaster in London , the East Anglican Ambulance Service has
launched a national "In case of Emergency (ICE)" campaign. In an emergency situation, Emergency Service personnel and hospital staff would then be able to quickly contact your next of kin, by simply dialing the number stored as "ICE".

It really could save your life, or put a loved one's mind at rest.

For more than one contact name simply enter
ICE1, ICE2 and ICE3 etc. 



A great idea that will make a difference!
Let's spread the concept of ICE by storing an ICE number
in our mobile phones today!

Thank You!
Let's make this happen!

Blue Tooth Technology

  • What Is Blue Tooth?
    Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras, and video game consoles over a secure, globally unlicensed short-range radio frequency. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group.
    Spectrum
    Bluetooth technology operates in the unlicensed industrial, scientific and medical (ISM) band at 2.4 to 2.485 GHz, using a spread spectrum, frequency hopping, full-duplex signal at a nominal rate of 1600 hops/sec. The 2.4 GHz ISM band is available and unlicensed in most countries
    List of applications
    More prevalent applications of Bluetooth include:
    • Wireless control of and communication between a cell phone and a hands-free headset or car kit. This was one of the earliest applications to become popular.
    • Wireless networking between PCs in a confined space and where little bandwidth is required.
    • Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
    • Transfer of files between devices with OBEX.
    • Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
    • Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment and traffic control devices.
    • For controls where infrared was traditionally used.
    • Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
    • Seventh-generation game consoles—Nintendo Wii[2], Sony PlayStation 3—use Bluetooth for their respective wireless controllers.
    Bluetooth Technology Benefits
    Why Choose Bluetooth wireless technology?
    Bluetooth wireless technology is the simple choice for convenient, wire-free, short-range communication between devices. It is a globally available standard that wirelessly connects mobile phones, portable computers, cars, stereo headsets, MP3 players, and more. Thanks to the unique concept of “profiles,” Bluetooth enabled products do not need to install driver software. The technology is now available in its fourth version of the specification and continues to develop, building on its inherent strengths — small-form factor radio, low power, low cost, built-in security, robustness, ease-of-use, and ad hoc networking abilities. Bluetooth wireless technology is the leading and only proven short-range wireless technology on the market today shipping over five million units every week with an installed base of over 500 million units at the end of 2005.
    Globally Available
    The Bluetooth wireless technology specification is available free-of-charge to our member companies around the globe. Manufacturers from many industries are busy implementing the technology in their products to reduce the clutter of wires, make seamless connections, stream stereo audio, transfer data or carry voice communications. Bluetooth technology operates in the 2.4 GHz, one of the unlicensed industrial, scientific, medical (ISM) radio bands. As such, there is no cost for the use of Bluetooth technology. While you must subscribe to a cellular provider to use GSM or CDMA, with Bluetooth technology there is no cost associated with the use beyond the cost of your device.
    Range of Devices
    Bluetooth technology is available in an unprecedented range of applications from mobile phones to automobiles to medical devices for use by consumers, industrial markets, enterprises, and more. The low power consumption, small size and low cost of the chipset solution enables Bluetooth technology to be used in the tiniest of devices. Have a look at the wide range products made available by our members in the Bluetooth product directory and the component product listing.
    Ease of Use
    Bluetooth technology is an ad hoc technology that requires no fixed infrastructure and is simple to install and set up. You don’t need wires to get connected. The process for a new user is easy – you get a Bluetooth branded product, check the profiles available and connect it to another Bluetooth device with the same profiles. The subsequent PIN code process is as easy as when you identify yourself at the ATM machine. When out-and-about, you carry your personal area network (PAN) with you and can even connect to others.
    Globally Accepted Specification
    Bluetooth wireless technology is the most widely supported, versatile, and secure wireless standard on the market today. The globally available qualification program tests member products as to their accordance with the standard. Since the first release of the Bluetooth specification in 1999, over 4000 companies have become members in the Bluetooth Special Interest Group (SIG). Meanwhile, the number of Bluetooth products on the market is multiplying rapidly. Volumes have doubled for the fourth consecutive year and are likely to reach an installed base of 500 million units by the close of 2005.
    Secure Connections
    From the start, Bluetooth technology was designed with security needs in mind. Since it is globally available in the open 2.4 GHz ISM band, robustness was built in from the beginning. With adaptive frequency hopping (AFH), the signal “hops” and thus limits interference from other signals. Further, Bluetooth technology has built-in security such as 128bit encryption and PIN code authentication. When Bluetooth products identify themselves, they use the PIN code the first time they connect. Once connected, always securely connected
    How Bluetooth Technology Works
    Bluetooth wireless technology is a short-range communications system intended to replace the cables connecting portable and/or fixed electronic devices. The key features of Bluetooth wireless technology are robustness, low power, and low cost. Many features of the core specification are optional, allowing product differentiation.
    The Bluetooth core system consists of an RF transceiver, baseband, and protocol stack. The system offers services that enable the connection of devices and the exchange of a variety of data classes between these devices.

    Overview of Operation
    The Bluetooth RF (physical layer) operates in the unlicensed ISM band at 2.4GHz. The system employs a frequency hop transceiver to combat interference and fading, and provides many FHSS carriers. RF operation uses a shaped, binary frequency modulation to minimize transceiver complexity. The symbol
    rate is 1 Megasymbol per second (Msps) supporting the bit rate of 1 Megabit per second (Mbps) or, with Enhanced Data Rate, a gross air bit rate of 2 or 3Mb/s. These modes are known as Basic Rate and Enhanced Data Rate respectively.
    During typical operation, a physical radio channel is shared by a group of devices that are synchronized to a common clock and frequency hopping pattern. One device provides the synchronization reference and is known as the master. All other devices are known as slaves. A group of devices synchronized in this fashion form a piconet. This is the fundamental form of communication for Bluetooth wireless technology.
    Devices in a piconet use a specific frequency hopping pattern which is algorithmically determined by certain fields in the Bluetooth specification address and clock of the master. The basic hopping pattern is a pseudo-random ordering of the 79 frequencies in the ISM band. The hopping pattern may be adapted to exclude a portion of the frequencies that are used by interfering devices. The adaptive hopping technique improves Bluetooth technology co-existence with static (non-hopping) ISM systems when these are co-located.
    The physical channel is sub-divided into time units known as slots. Data is transmitted between Bluetooth enabled devices in packets that are positioned in these slots. When circumstances permit, a number of consecutive slots may be allocated to a single packet. Frequency hopping takes place between the transmission or reception of packets. Bluetooth technology provides the effect of full duplex transmission through the use of a time-division duplex (TDD) scheme.
    Above the physical channel there is a layering of links and channels and associated control protocols. The hierarchy of channels and links from the physical channel upwards is physical channel, physical link, logical transport, logical link and L2CAP channel.
    Within a physical channel, a physical link is formed between any two devices that transmit packets in either direction between them. In a piconet physical channel there are restrictions on which devices may form a physical link. There is a physical link between each slave and the master. Physical links are not formed directly between the slaves in a piconet.
    The physical link is used as a transport for one or more logical links that support unicast synchronous, asynchronous and isochronous traffic, and broadcast traffic. Traffic on logical links is multiplexed onto the physical link by occupying slots assigned by a scheduling function in the resource manager.
    A control protocol for the baseband and physical layers is carried over logical links in addition to user data. This is the link manager protocol (LMP). Devices that are active in a piconet have a default asynchronous connection-oriented logical transport that is used to transport the LMP protocol signaling. For historical reasons this is known as the ACL logical transport. The default ACL logical transport is the one that is created whenever a device joins a piconet. Additional logical transports may be created to transport synchronous data streams when this is required.
    The link manager function uses LMP to control the operation of devices in the piconet and provide services to manage the lower architectural layers (radio layer and baseband layer). The LMP protocol is only carried on the default ACL logical transport and the default broadcast logical transport.
    Above the baseband layer the L2CAP layer provides a channel-based abstraction to applications and services. It carries out segmentation and reassembly of application data and multiplexing and de-multiplexing of multiple channels over a shared logical link. L2CAP has a protocol control channel that is carried over the default ACL logical transport. Application data submitted to the L2CAP protocol may be carried on any logical link that supports the L2CAP protocol.

Donot Use mobile While Driving

If you drive using a mobile phone you are four times more likely to crash, than someone not using a phone.
 
                          

Using a mobile phone while driving reduces your ability to react and distracts your concentration. This applies equally to conversations on hand-held and hands-free phones.
 
Some studies have shown that using a mobile phone while driving can affect your ability as much as being over the drink-drive limit.
Having a mobile phone conversation increases drivers' mental workload and stress levels.
Using a mobile phone while driving affects your ability to:
  • stay in lane
  • keep to a steady speed
  • keep to the speed limit
  • stay a safe distance from the vehicle in front
Using a mobile phone while driving also affects your:
  • reaction times
  • judgement of safe gaps
  • general awareness of other traffic
Research shows using a mobile phone while driving can lead to more aggressive driving behaviour.
 
Hands-free mobile calls still affect your driving ability; reducing awareness and increasing reaction times.
 
You can still be prosecuted for dangerous driving when using a hands-free mobile phone.